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THCALC.TXT
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1991-02-24
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Thermo Calc
~~~~~~~~~~~~~
Thermocouple Calculator
~~~~~~~~~~~~~~~~~~~~~~~~~
I. Introduction.
II. Main menu.
III. Manual calculation.
IV. Automatic calculation.
V. Valid keyboard inputs.
VI. Small print.
I Thermo Calc
~~~~~~~~~~~~~
Thermo Calc is intended as an aid for anyone who uses thermocouples. It
will calculate the EMF generated by any of the standard thermocouples at any
temperature within their specified ranges; or will calculate the temperature
if the EMF is known. Thermo Calc can, therefore, be used by people
calibrating or designing thermometers based on thermocouples, or people who
wish to use thermocouples directly into a voltmeter without any intervening
electronics.
The formulae used by Thermo Calc are based on BS 4937, for which full
credit is acknowledged. The formulae are claimed to give errors no greater
than the least significant digit in the BS 4937 tables. This should, in
theory, ensure that any results obtained by this program can be considered to
be correct for all practical purposes. (If anyone discovers otherwise PLEASE
let me know).
II MAIN MENU
~~~~~~~~~~~
The main menu in Thermo Calc is used both to select the various options,
like thermocouple type or temperature scale, and to initiate the different
modes of operation, like manual or automatic calculation.
Menu items are selected either by using the vertical curser controls to
highlight the required item, or by pressing the appropriate number key. Once
an option item has been selected, the option can be changed either by using
the horizontal curser keys, or in some cases by pressing a letter key. Brief
instructions are given at the bottom of the screen for each item. Details of
each item are as follows.
1. Help
This item invokes the Help mode and, basically, displays or prints these
pages.
2. Exit to DOS
Exit from Thermo Calc to DOS (or whatever shell is in use).
3. Manual calculation
This starts the normal mode of operation in which the user inputs a
temperature or a voltage and Thermo Calc calculates the other (depending on
the setting of the Direction option).
4. Automatic calculation
This mode is more useful if the user wishes to create a mini table of
results. (The original BS 4937 tables are obviously better if more than a few
values are required.) Thermo Calc prompts for a starting value, an end value
and a step size. It then performs the required calculations automatically. It
is advisable to enable the printer option before using this mode.
5. Change direction
This is one of the option items, with just two options; temperature to
voltage or voltage to temperature. The default is temp.>volts in which case
the user inputs a temperature and Thermo Calc calculates the corresponding
voltage. Either of the horizontal curser keys, or the RETURN key, just toggle
between the two options.
6. Printer output
This is another two option item; enabled or disabled. The default is
disabled, in which case the results are displayed on the screen only. If this
option is enabled then results are also output to a printer (assuming one is
connected of course).
7. Select temperature scale
This item has four options; C,F,K,R; (Celsius, Fahrenheit, Kelvin and
Reaumer). The default is C. The horizontal curser keys scroll through the
options, or the choice can be made directly by pressing the appropriate
letter key.
8. Select thermocouple type
This item is used to select the thermocouple type in a similar manner to the
temperature scale. The options are S,R,J,K,T,E,B,N; the default being K.
Again, the letter key can be pressed directly or the options can be scrolled
through with the horizontal curser keys. In either case, not only is the
letter displayed, but also the thermocouple composition and the corresponding
part number of BS 4937.
III MANUAL CALCULATION
~~~~~~~~~~~~~~~~~~~~
To start manual calculation: after changing any options if required,
highlight item 3 in the main menu and press return. Manual calculation is the
normal mode of operation for Thermo Calc. It accepts any valid input entered
via the keyboard and immediately displays the result.
Firstly it displays a header showing the current settings of all the
options and then prompts you for an input. If the input is valid (see section
headed Valid Keyboard Inputs) it then displays both the input and the result
in two columns. (The reason it redisplays the input is that it does so in a
consistent, readable format, acting as a visual check on the input and
tidying up the printout if enabled). If the printer option has been enabled
then the header and both columns are also printed. If the input is invalid
then a warning message is displayed (and printed). If the input is only just
outside the valid range then a result is given along with a message to the
effect that the result is only approximate.
When you have finished, or to change any of the options, press RETURN with
no input. This returns you to the main menu. BUT REMEMBER, any results not
printed will be lost. Also, any results which scroll off the top of the
screen will be lost, so it is advisable to enable the printer if more than a
screen full of results are expected. The contents of the screen can, of
course, be printed at any time by pressing the Prt Sc key.
IV AUTOMATIC CALCULATION
~~~~~~~~~~~~~~~~~~~~~~~
This mode works in a similar manner to the manual mode but Thermo Calc
supplies the inputs. To start this mode, highlight item 6 and press RETURN.
Thermo Calc will then display (and print if enabled) the header and prompt
you for three pieces of information: start, end and interval. For example, If
you want the results for all values from 50 to 100 in steps of 0.5 then enter
50 as the start value, 100 as the end and 0.5 as the interval. Thermo Calc
then interprets your input but does not check for out of range values at this
stage (see Valid Keyboard Inputs). Thermo Calc then asks you to confirm your
input and, if OK, performs all the calculations automatically, displaying
(and printing) the results in two columns. It is at this stage that out of
range warnings are issued.
Because of it's automatic nature, and the fact that any results scrolled
off the screen will be lost, it is advisable to always enable the printer
option before using this mode; assuming, of course, that you have a printer
connected.
V VALID KEYBOARD INPUTS
~~~~~~~~~~~~~~~~~~~~~~~
Thermo Calc is fairly versatile in what inputs it will accept, but not
limitless. You can use normal numbers (E.G. 0.0015 or 2300), you can use
scientific notation (E.G. 1.5e-3 or 2.3e3), or you can use a suffix letter
(E.G. 1.5m or 2.3k). When using a suffix Thermo Calc will accept
f,p,n,u,m,k,M,G or T. It will even accept the Greek letter µ (mu) if you want
to be pedantic! Anything after the first letter is ignored so 1.5m is
sufficient for 1.5 mV. The suffix must NOT be placed in the middle of the
number, I.E.- 2k3 is NOT valid and will be interpreted as 2k. Commas must NOT
be included. 2,300 will be interpreted as 2.
Temperature inputs must be in the selected temperature scale. To change
the scale use item 7 in the main menu. All inputs must be within the
specified range, although inputs just outside the limits will be accepted and
a warning displayed. The valid range is displayed in the header.
VI SMALL PRINT
~~~~~~~~~~~~~
Thermo Calc is intended to be User Supported, which means you are free to
use it, copy it and pass it on to anyone on a trial basis. However, if you
find it useful then a financial contribution to the author would be in order.
Companies should send £50 but if you are a private individual just send
whatever you think the program is worth to you. (Contributors will receive a
copy of the latest version of this program and maybe others I happen to have
lying around at the time!) There is no printed manual available (you
shouldn't need one!) and there is no official after sale support. However, if
you are able to get in touch with me then I will give any assistance I can.
Suggestions and corrections will be accepted just as enthusiastically as
money (well almost!).
Roly Williams
22 Morrison Drive
Lennoxtown
Strathclyde
G65 7BA
Phone; 0360-31157